Enable path specification for project creation (ENG-384, supersedes #76)

[tino097]

Description

Rebased continuation of #76 — original work by @MinuraPunchihewa (authorship preserved in the commits), rebased onto current staging. #76 stays open for its review history; please review here.

• Enables a path to be specified when creating a project, so a project can point at an existing local folder.
• Stores project instructions on the Project record (DB) instead of .anton/anton.md, so they reach every harness (Anton and Hermes).
• Renaming a project no longer moves its directory — the path may be a user-chosen folder outside the projects root. Skill-metadata sync on rename (from staging) is preserved.

Changes on top of the original #76 branch:

• Re-chained the add_project_instructions migration onto the current staging head d5f3a8c1e6b2 — it remains a single clean migration and the alembic graph has a single head (verified via alembic heads and a full-chain upgrade on a scratch DB, both fresh-create and pre-alembic upgrade paths).
• Fixed tests/test_schema_migrations.py: the simulated pre-alembic DB is built from current models, so it must drop the new instructions column — same convention the test already uses for messages.harness and the channel tables.

Linear: ENG-384
Front-end PR: mindsdb/cowork#340 (supersedes mindsdb/cowork#210)

Merge order: this PR first, then the cowork front-end PR.

Testing

• uv run pytest: 309 passed. The 6 failures in test_publish_versions.py are pre-existing on staging (verified identical on a pristine staging worktree; local anton wheel lacks activate_version).
• Service-level smoke: create pointing at an existing folder (contents preserved), instructions persisted/updated/cleared, default-path creation unchanged, rename never moves the folder.

🤖 Generated with Claude Code

[tino097]

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